Thanksgiving week promises snow—but after that, it’s anybody’s guess

Sun Valley’s snow guns haven’t gotten much help from the skies as they prep Bald Mountain for its Thanksgiving opening next week. October snowfall gave way to a bluebird November in the mountains of central Idaho—but things might change just in time for the season’s first turns.

The National Weather Service expects the high-pressure system that shone through the month to break up late Sunday or early Monday morning, giving way to progressively colder temperatures and scattered snowfall at higher elevations, according to Dawn Harmon, a senior meteorologist at the Pocatello office.

“The weather is about to change,” she said. “We’ll have a pleasant weekend, but I think skiers will be pleased with the upcoming week.”

Travelers less so. Thanksgiving trekkers will need to be patient—and, ideally, flexible—with the sporadic precipitation dropped by the “unsettled” air churning into the area. That’s the pattern after the holiday, too; Harmon expects to see movement for the next several weeks, including a series of low-pressure systems sweeping into the mountain West. Translation: Sun Valley’s snow makers should get the boost they need.

“I have decent confidence that the trend will be colder and wetter,” Harmon said. “It definitely looks like a pretty decent start to December.”

“Decent” is about as forceful an endorsement as you’ll get from trained meteorologists, who know that the outlook can change drastically between the time a reporter hangs up the phone and when his story’s set in ink. They deal in probability, not certainty.

“It’s a numbers game, like flipping a coin or rolling dice,” Harmon said. “You’re playing the odds.”

Long term, those are more likely to be warmer and wetter than average, according to the 90-day winter outlook for the area released by the federal Climate Prediction Center on Thursday morning. Its forecast looks “pretty confident” that our part of Idaho is in line for above-normal temperatures and precipitation, Harmon said.

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“It’s a numbers game, like flipping a coin or rolling dice You’re playing the odds.”Dawn Harmon, National Weather Service

“How far above normal, they can’t say,” she said. “This is a three-month average—it doesn’t preclude big changes right in the middle. On balance, though, it could be great for skiing.”

But Harmon warns not to put too much stock in its predictive power. The process starts in College Park, Md., where meteorologists start running simulations using a model for the months in question. They begin with the assumption that average, above average and below average outcomes are all equally likely—a 33.3 percent chance of each. If the simulations say otherwise, they’ll weight each percentage up or down. So, all the forecast says is that we’re more likely to see above-average temperatures and moisture than we are average or below-average values. That doesn’t even mean it’s likely to happen—just that it’s the most likely of the three.

“Unfortunately, there is virtually no confidence in any seasonal, three-to-six-month prediction,” said Joel Gratz, a meteorologist and the founder of OpenSnow.com, which specializes in forecasting ski conditions. His site doesn’t even try to furnish an official long-range outlook—more than 10 days out, you can’t do it with any degree of certainty.

In August, the site published a post-mortem on forecasts that tried to predict the 2018-19 season. It looked at more than a dozen models. Some got pieces correct, but none were on-the-nose accurate. The closest one was arguably the least scientific—The Old Farmer’s Almanac, which called for a wet year nationwide.

Good news for skiers there: It’s calling for “low temps, deep powder” in southern Idaho, with “a parade of snowstorms” up north.

Gratz does see some snow in Sun Valley’s immediate future, with a sign of a “promising” December. Of course, it can all change on the wind. Until the snow starts to fly, all skiers can do is wax up the boards, make sure their snow pants still fit and cross their fingers.

“The reality about the question of how much will it snow this season,” Gratz said, “is that we just don’t know!”

Sun Valley set for Thanksgiving open

The first chair of the season will head up Bald Mountain from River Run at 9 a.m. on Thanksgiving Day, Nov. 28. Sun Valley hasn’t announced which trails will be open on opening day, but Dollar Mountain won’t be ready for a November opening. Check back early next week, or read Wednesday’s edition of the Idaho Mountain Express for a full rundown.